This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 2000-313010 filed on Oct. 13, 2000, the entire content of which is incorporated herein by reference.
The present invention is generally directed to a synchromesh-type transmission of a vehicle. More particularly, the present invention pertains to an actuator control for a shifting device in a synchromesh-type vehicle transmission.
One known type of vehicle transmission is a synchromesh-type transmission which transmits a rotation from a source of power to the driving wheels in an automotive vehicle. In this type of transmission, the power transmission path extending from the source of power to each of the driving wheels includes no sliding parts or components. Thus, unlike automatic transmissions, synchromesh-type transmissions have the advantage that a highly responsive driving feeling can be obtained resulting from a relatively quick response of the driving wheels when the driver depresses the acceleration pedal. In addition, fuel or gas consumption can be reduced, thus contributing to energy savings.
To make the driver""s gear shift or changing gear ratio much easier than that in the conventional fully manually operated transmission, while also enjoying the above-mentioned advantages, techniques have been developed for changing the gear ratio of a synchromesh type transmission through operation of an electrically controlled actuator. One example is disclosed in Japanese Unexamined Patent Publication No. 2000-46176.
The transmission which is in association with a shifting device of the kind includes a synchromesh mechanism in which one of a plurality of continually meshed gear pairs of different gear ratios is selected as a valid gear pair.
The synchromesh mechanism includes a sleeve and a synchronizer ring. The sleeve is rotatable together with the shaft and is movable in the axial direction of the shaft on which one of the gear pair is mounted as an idle gear, which is free to rotate relative to the shaft. The synchronizer ring is free to rotate and move in an axial direction relative to the idle gear.
When the synchromesh mechanism is made active, synchronization is established between the idle gear and the sleeve by moving the sleeve in the axial direction to engage the synchronizer ring to thereby causing the synchronizer ring to push on a frictional surface which is incapable of rotating relative to the idle gear and a balk is established until the synchronization is completed which prevents a clutch which is incapable of rotating relative to the sleeve from being engaged with another clutch which is incapable of rotating relative to the idle gear.
The above-mentioned shifting device includes an actuator and a control device, with the actuator being controlled electrically in response to an external signal to generate a load for moving the sleeve in the axial direction. The control device feeds a driving signal to the actuator to change the gear ratio of the transmission on the basis of the driver""s intention and the state of the vehicle.
The shifting device should preferably be designed to change the gear ratio of the transmission without an improper feeling. To address this need, it is desirable to control the synchronization time duration as the time passing duration ranging from initiation to termination of each synchronization operation in the transmission in such a manner that actual synchronization time durations are made stable or equalized when plural synchronization operations are performed.
The present invention provides an improved shifting device associated with a synchromesh-type transmission for changing the gear ratio of the transmission which transmits rotation from a power source to driving wheels. The transmission includes a synchromesh mechanism having a plurality of constantly meshed gear pairs possessing different gear ratios, with one of the gear pairs being selected as an effective gear pair. The synchromesh mechanism also has a sleeve and a synchronizer ring, with the sleeve being mounted on a shaft on which one of each of the gear pairs is mounted as an idle gear. The sleeve is rotatable together with the shaft and is movable in the axial direction of the shaft. The synchronizer ring is rotatable and movable relative to the idle gear, and the synchromesh mechanism is brought into operation to establish synchronization between the idle gear and the sleeve in such a manner that the sleeve is moved in the axial direction to be engaged with the synchronizer ring, and subsequently the engaged synchronizing ring is urged onto a friction surface of the idle gear so as to be rotatable together with the idle gear. The shifting device includes an electrically controlled actuator generating a load for acting on the sleeve to move the sleeve in the axial direction in response to a driving signal, and a control device outputting the driving signal to the actuator upon current synchronization control to change the gear-ratio of the transmission on the basis of at least one of the vehicular driver""s intention, the state of the vehicle, and the state of the transmission. The control device includes a driving signal determination mechanism for determining the driving signal on the basis of an initial relative rotation number and a relative rotation number deviation. The initial relative rotation number being is as a relative rotation between the idle gear and the sleeve at initiation of the current synchronization control. The relative rotation number deviation is a deviation between a target relative rotation number and an actually detected relative rotation number. The target relative rotation number is between the idle gear and the sleeve at the latest synchronization control, while the actually detected relative rotation number is between the idle gear and the sleeve at the latest synchronization control.
Theoretically speaking, in a typical synchromesh-type transmission, a fixed relation is found between the initial relative rotation number, the synchronization time duration, and the sleeve load, so that the initial relative rotation number is the relative rotation number between the idle gear and the sleeve at an initiation of a specific synchronization, the synchronization time duration is the elapsed time duration from the initiation to termination of the synchronization, and the sleeve load is a load applied to the sleeve from an actuator. Thus, if a predetermined synchronization time duration is employed as the target synchronization time duration, based thereon, the sleeve load is determined or decided relative to the initial relative rotation number and consequently a suitable driving signal is applied to the actuator for realizing the determined sleeve load. In such a way, the initial relative rotation number is an effective or a valid physical quantity for determining the driving signal throughout the synchronization control.
Moreover, an error in the driving signals in the latest or previous synchronization control is reflected in the relative rotation number deviation which is the deviation of the actual relative rotation number in the latest synchronization control from the target relative rotation number. Thus, taking into account the relative rotation number deviation in the latest synchronization control makes it possible to make the relation between the initial rotation number and the driving signal more adequate or appropriate in each synchronization control.
In view of the above, in the shifting device here, the driving signal to be applied to the actuator in each synchronization control is determined on the basis of the initial relative rotation number in each synchronization control and the relative rotation number deviation in the latest synchronization control. Thus, despite that the driving signal which governs the entirety of each synchronization is determined on the basis of the initial relative rotation number, the control error in the latest synchronization control is fed back to the next synchronization control, and so the driving signal for the next synchronization control is determined with much higher precision. Therefore, the shifting device here make it possible to stabilize the actually required time duration for each synchronization when a plurality of synchronizations are performed.
Considering the relative rotation number deviation in the latest synchronization control, a specific value at a point in time in the latest synchronization control which is representative of the entire latest synchronization control or a history of the relative rotation number deviation throughout the latest synchronization control can be utilized. With respect to the history of the relative rotation number deviation throughout the latest synchronization control, examples can include an integral value of a relative rotation number deviation in the latest synchronization control, a differential value thereof, a summation of a plurality of successively obtained relative rotation number deviations in the latest synchronization control, and an average of the plurality of successively obtained relative rotation number deviations in the latest synchronization control.
The power source utilized here may be an internal combustion engine, an electric motor, or a combination of the engine and the electric motor. Also, the control device can be of a type in which the actuator is made controlled mainly by an output signal issued from a sensor which detects the driver""s intention, particularly the driver""s gear shift intention with respect to a shift lever or the like. The control device can also be of a type in which the actuator is controlled mainly by output signals of respective sensors, with one of the sensors being a sensor which detects the driver""s intention, particularly the driver""s vehicle acceleration/deceleration intention such as indicated by an acceleration pedal or the like. Another sensor can detect the vehicle""s state such as the vehicle speed or the power source rotation number.
In general, vehicles on which a synchromesh-type transmission is provided include a clutch to engage and disengage the power source and the synchromesh-type transmission. The clutch can be two types, one operated directly by the driver, the other operated by an electrically controlled actuator. If the automatic type clutch is employed, the control device used here can be of a type in which the control device is in association with an actuator which controls an actuator and also controls a clutch of the actuator.
The synchromesh mechanism is employed in the same transmission and is constructed in such a manner that one of the gear pairs is selected as an effective gear pair. In addition, the actuator can be an electrically operated driving source utilizing type or a pressure source utilizing type. The electrically operated driving source utilizing type is an actuator which is operated by controlling an electrical driving source or a control device coupled thereto, while the pressure source utilizing type is an actuator which is operated by controlling a pressure source such as a pump or accumulator for generating a pressure and an electromagnetic valve or the like coupled thereto.
The present shifting device can be adopted in a transmission in which the shaft and the power source are coupled to the driving wheels and the non-idle gear, respectively. The shifting device can also be adopted in a transmission in which the shaft and the non-idle gear are coupled to the power source and the driving wheels, respectively.
In the shifting device, the relative rotation number deviation is defined by at least one of an overall value of the relative rotation number deviation in the latest synchronization control, a synchronization time duration deviation between an actual synchronization time duration ranging from initiation to completion of the latest synchronization and a target synchronization time duration, an elapsed time relative rotation number deviation as an actual relative rotation number which is to be zero when the target synchronization time duration elapsed in the latest synchronization control, and a change gradient deviation between an actual relative rotation number change gradient in the latest synchronization control and a target relative rotation number change gradient.
The relative rotation number deviation in the first aspect can be defined or determined by an overall value of the relative rotation number deviation in the latest synchronization control. In addition, the relative rotation number deviation can be defined or determined by the synchronization time duration between the actual and target synchronization time durations in the latest synchronization control. The reason is that whether the actual synchronization time duration is shorter or longer than the target synchronization time duration involves consideration of whether the time when the actual relative rotation number becomes zero is prior to or later than the scheduled time. Moreover, the relative rotation number deviation can be defined or determined by the elapsed time relative rotation number deviation which is to be zero when the target synchronization time duration elapsed in the latest synchronization control. Further, the relative rotation number deviation can be defined or determined by the change gradient deviation between the actual relative rotation number change gradient in the latest synchronization control and the target relative rotation number change gradient.
The relative rotation number deviation can be defined or determined by one of the overall value of relative rotation number deviation, the synchronization time duration deviation, and the change gradient deviation. The overall value can be, for example, a time-related integrated value of the relative rotation number deviation in the latest synchronization control or a summation of a plurality of intermittently obtained relative rotation numbers in the latest synchronization control.
The driving signal determination mechanism has a signal determining portion which determines the driving signal corresponding to an actual initial relative rotation number at each synchronization control pursuant to a relation between the initial relative rotation number and the driving signal, and a relation-correcting portion performing a correction on the basis of the relative rotation number deviation at the latest synchronization control, prior to the current synchronization control, in such a manner that the resultant (i.e., corrected relation) makes an actual synchronizing time duration between initiation and termination of the current synchronization control much closer to a target synchronizing time duration.
The driving signal corresponding to the actual initial relative rotation number at each synchronization control is determined pursuant to the relation between the initial relative rotation number and the driving signal, and prior to the current synchronization control a relation-correction is performed in such a manner that the resultant (i.e., the corrected relation) makes the actual synchronizing time duration between the initiation and the termination of the current synchronization control much closer to the target synchronizing time duration. The relation between the initial rotation number and the driving signal in the current synchronization control is corrected so that the target synchronization time duration of each synchronization control is more precise by feeding back the relative rotation number deviation in the latest synchronization control. Thus, it is possible to put the shifting device into practice in a preferable mode by correcting the current relation between the initial rotation number and the driving signal in the latest synchronization control.
The relative rotation number deviation is defined on the basis of at least one of: an overall value of the relative rotation number in the latest synchronization control; a synchronization time duration deviation of an actual synchronization time duration between initiation and completion of the latest synchronization relative a target synchronization time duration; an elapsed time relative rotation number deviation as an actual relative rotation number which is to be zero when the target synchronization time duration elapsed in the latest synchronization control; and a change gradient deviation between an actual relative rotation number change gradient in the latest synchronization control and a target relative rotation number change gradient. The relation-correcting portion corrects the relation in such a manner that at least one of the overall value, the synchronization time duration deviation, the elapsed time relative rotation number deviation, and the change gradient deviation are made close to zero.
The correction of the relation between the initial relative rotation number and the driving signal is performed in such a manner that one of the overall value, the synchronization time duration deviation, the elapsed time relative rotation number deviation, and the change gradient deviation is made close to zero, resulting in that the corrected relation determines the driving signal in such a manner that the actual synchronization time duration ranging from its initiation to completion approaches the target synchronization time duration.
According to another aspect of the invention, the relation-correcting portion corrects the relation on the basis of at least two of the overall value, the synchronization time duration deviation, the elapsed time relative rotation number deviation, and the change gradient deviation. This results in the correction precision being improved relative to when the correction is based on one of the overall value, the synchronization time duration deviation, the elapsed time relative rotation number deviation, and the change gradient deviation.
The relation-correcting portion can also correct the relation, prior to an initiation of a new synchronization control, on the basis of the relative rotation number deviation and an actual driving signal in the latest synchronization control.
When the correction of the relation between the initial relative rotation number and the driving signal is based on the actual driving signal in addition to the relative rotation number deviation, the resultant correction can be made with higher precision than a correction based on only the relative rotation number deviation.
In view of the above, prior to a new or current synchronization control, a correction of the relation is made based on the relative rotation number deviation and the actual driving signal in the latest synchronization control.
With respect to the actual driving signal in the latest synchronization control, a specific value at a time point in the latest synchronization control which is representative of the entire latest synchronization control or a history of the relative driving signal throughout the latest synchronization control can be employed by way of example. With respect to the history of the driving signal throughout the latest synchronization control, examples include an integral value (level) of signal fed to the actuator in the latest synchronization control, a differential value thereof, a summation of a plurality of successively applied values (levels) of signals fed to the actuator in the latest synchronization control, and an average of the plurality of successively applied values (levels) of signals fed to the actuator in the latest synchronization control.
The shaft is operatively connected to the driving wheels, the other of the gear pairs is operatively connected as a non-idle gear to the power source, and the relative rotation number is obtained as an input rotation number, i.e., the rotation number of the idle gear. The shaft and the idle gear in the synchromesh mechanism are connected to the driving wheels and the power source, respectively. If a comparison is made between the driving wheel and the power source from the viewpoint of rotation stability, the driving wheel is of a strong tendency to be rotated at constant speeds, while the power source is not so or is weak. Thus, when the driving wheel is connected to the shaft which is impossible to rotate relative to the sleeve and when the power source is connected to the non-idle gear which is continually in meshing engagement with the idle gear, there is a tendency in which a time-series change in relative rotation number between the sleeve and the idle gear is in coincidence with a time-series change in rotation number of the idle gear.
When the shaft and the non-idle gear are connected to the driving wheels and the power source, respectively, the relative rotation number is obtained as the rotation number of the idle gear, i.e., the input rotation number. Thus, in the present shifting device, the relative rotation number can be easily obtained when compared to a structure in which the shaft and the non-idle gear are connected to the driving wheels and the power source, respectively, and the relative rotation number is obtained as a deviation between the rotation number of idle gear (i.e., the input rotation number) and the rotation number of the sleeve (i.e., the output rotation number).